SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "L773:1352 2310 srt2:(2010-2011)"

Sökning: L773:1352 2310 > (2010-2011)

  • Resultat 11-20 av 20
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
11.
  • Mercer, Laina D., et al. (författare)
  • Comparing universal kriging and land-use regression for predicting concentrations of gaseous oxides of nitrogen (NOx) for the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air)
  • 2011
  • Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 45:26, s. 4412-4420
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Epidemiological studies that assess the health effects of long-term exposure to ambient air pollution are used to inform public policy. These studies rely on exposure models that use data collected from pollution monitoring sites to predict exposures at subject locations. Land-use regression (LUR) and universal kriging (UK) have been suggested as potential prediction methods. We evaluate these approaches on a dataset including measurements from three seasons in Los Angeles, CA. Methods: The measurements of gaseous oxides of nitrogen (NOx) used in this study are from a "snapshot" sampling campaign that is part of the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air). The measurements in Los Angeles were collected during three two-week periods in the summer, autumn, and winter, each with about 150 sites. The design included clusters of monitors on either side of busy roads to capture near-field gradients of traffic-related pollution. LUR and UK prediction models were created using geographic information system (GIS)-based covariates. Selection of covariates was based on 10-fold cross-validated (CV) R-2 and root mean square error (RMSE). Since UK requires specialized software, a computationally simpler two-step procedure was also employed to approximate fitting the UK model using readily available regression and GIS software. Results: UK models consistently performed as well as or better than the analogous LUR models. The best CV R-2 values for season-specific UK models predicting log(NOx) were 0.75, 0.72, and 0.74 (CV RMSE 0.20, 0.17, and 0.15) for summer, autumn, and winter, respectively. The best CV R-2 values for season-specific LUR models predicting log(NOx) were 0.74, 0.60, and 0.67 (CV RMSE 0.20, 0.20, and 0.17). The two-stage approximation to UK also performed better than LUR and nearly as well as the full UK model with CV R-2 values 0.75, 0.70, and 0.70 (CV RMSE 0.20, 0.17, and 0.17) for summer, autumn, and winter, respectively. Conclusion: High quality LUR and UK prediction models for NOx in Los Angeles were developed for the three seasons based on data collected for MESA Air. In our study, UK consistently outperformed LUR. Similarly, the 2-step approach was more effective than the LUR models, with performance equal to or slightly worse than UK. (C) 2011 Elsevier Ltd. All rights reserved.
  •  
12.
  • Mills, Gina, 1959, et al. (författare)
  • New stomatal flux-based critical levels for ozone effects on vegetation
  • 2011
  • Ingår i: Atmospheric Environment. - : Elsevier BV. - 1873-2844 .- 1352-2310. ; 45:28, s. 5064-5068
  • Tidskriftsartikel (refereegranskat)abstract
    • The critical levels for ozone effects on vegetation have been reviewed and revised by the LRTAP Convention. Eight new or revised critical levels based on the accumulated stomatal flux of ozone (POD gamma, the Phytotoxic Ozone Dose above a threshold flux of Y nmol m(-2) PLA s(-1), where PLA is the projected leaf area) have been agreed. For each receptor, data were combined from experiments conducted under naturally fluctuating environmental conditions in 2-4 countries, resulting in linear dose response relationships with response variables specific to each receptor (r(2) = 0.49-0.87, p
  •  
13.
  • Nilsson, S, et al. (författare)
  • Endotoxins in urban air in Stockholm, Sweden
  • 2011
  • Ingår i: ATMOSPHERIC ENVIRONMENT. - : Elsevier BV. - 1352-2310. ; 45:1, s. 266-270
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
  •  
14.
  • Peichl, Matthias (författare)
  • Evaluating management effects on nitrous oxide emissions from grasslands using the process-based DeNitrification-DeComposition (DNDC) model
  • 2011
  • Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 45, s. 6029-6039
  • Tidskriftsartikel (refereegranskat)abstract
    • The development of agricultural mitigation strategies to reduce greenhouse gas (GHG) emissions is urgent in the context of climate change - land use interactions. In this study the DNDC biogeochemical model was used to study nitrous oxide (N(2)O) emissions from grazed grasslands in southern Ireland. The objectives of this study were: (1) to evaluate the DNDC model using a two year (2008-2009) data set of chamber measured N(2)O fluxes at eight grassland sites and (2) to investigate the impact of different management scenarios on N(2)O emissions including changes in i) inorganic nitrogen (N) fertilizer application rates ii) slurry application rates; and iii) animal density (livestock unit per hectare LU ha(-1)). The comparison of modeled daily DNDC fluxes (using a combination of measured and default soil parameters) and measured fluxes resulted in an r (coefficient correlation) = 0.48. To improve the model performance, the fluxes for 2008 were used in a calibration exercise during which the soil properties were optimized to obtain the best fit of N(2)O fluxes. This resulted in an improved model performance, with an r = 0.62. In a validation exercise using 2009 data, we used the model parameters set (e.g. soils) from the calibration exercise and this resulted in a model performance with an r = 0.57. The annual N(2)O fluxes (measured and modeled) were appreciably higher than those estimated using the IPCC emissions factor of 1.25%. In scenario analysis, the modeled N(2)O fluxes only increased/decreased on average +/-6% and +/-7% following a 50% increase/decrease of inorganic N and slurry N applications respectively. These modeled scenario % changes are much lower than the IPCC emission factor % changes of a 50% increase in N(2)O emissions for a 50% increase in nitrogen applied. An absolute change scenario (+/-50 kg) in inorganic N and slurry N resulted in greater change in N(2)O fluxes (+/-9% inorganic N and +/-17% slurry N) as compared to the relative change scenario (above). Furthermore, DNDC N(2)O flux estimates were not sensitive to changes in animal density (LU ha(-1)). The latter is a scenario limitation in the current model version. This study suggests that the calibration of soil parameters for Irish conditions is necessary for optimum simulation with DNDC and highlights the potential of management strategies for reducing N(2)O emissions from grazed grasslands. It further highlights the difference between DNDC and IPCC estimates that require further research. Published by Elsevier Ltd.
  •  
15.
  • Putaud, J. -P, et al. (författare)
  • A European aerosol phenomenology-3 : Physical and chemical characteristics of particulate matter from 60 rural, urban, and kerbside sites across Europe
  • 2010
  • Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 44:10, s. 1308-1320
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper synthesizes data on aerosol (particulate matter, PM) physical and chemical characteristics, which were obtained over the past decade in aerosol research and monitoring activities at more than 60 natural background, rural, near-city, urban, and kerbside sites across Europe. The data include simultaneously measured PM10 and/or PM2.5 mass on the one hand, and aerosol particle number concentrations or PM chemistry on the other hand. The aerosol data presented in our previous works (Van Dingenen et al., 2004; Putaud et al., 2004) were updated and merged to those collected in the framework of the EU supported European Cooperation in the field of Scientific and Technical action COST633 (Particulate matter: Properties related to health effects). A number of conclusions from our previous studies were confirmed. There is no single ratio between PM2.5 and PM10 mass concentrations valid for all sites, although fairly constant ratios ranging from 0.5 to 0.9 are observed at most individual sites. There is no general correlation between PM mass and particle number concentrations, although particle number concentrations increase with PM2.5 levels at most sites. The main constituents of both PM10 and PM2.5 are generally organic matter, sulfate and nitrate. Mineral dust can also be a major constituent of PM10 at kerbside sites and in Southern Europe. There is a clear decreasing gradient in SO42- and NO3- contribution to PM10 when moving from rural to urban to kerbside sites. In contrast, the total carbon/PM10 ratio increases from rural to kerbside sites. Some new conclusions were also drawn from this work: the ratio between ultrafine particle and total particle number concentration decreases with PM2.5 concentration at all sites but one, and significant gradients in PM chemistry are observed when moving from Northwestern, to Southern to Central Europe. Compiling an even larger number of data sets would have further increased the significance of our conclusions, but collecting all the aerosol data sets obtained also through research projects remains a tedious task.
  •  
16.
  • Sampson, Paul D., et al. (författare)
  • Pragmatic estimation of a spatio-temporal air quality model with irregular monitoring data
  • 2011
  • Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 45:36, s. 6593-6606
  • Tidskriftsartikel (refereegranskat)abstract
    • Statistical analyses of health effects of air pollution have increasingly used GIS-based covariates for prediction of ambient air quality in "land use" regression models. More recently these spatial regression models have accounted for spatial correlation structure in combining monitoring data with land use covariates. We present a flexible spatio-temporal modeling framework and pragmatic, multi-step estimation procedure that accommodates essentially arbitrary patterns of missing data with respect to an ideally complete space by time matrix of observations on a network of monitoring sites. The methodology incorporates a model for smooth temporal trends with coefficients varying in space according to Partial Least Squares regressions on a large set of geographic covariates and nonstationary modeling of spatio-temporal residuals from these regressions. This work was developed to provide spatial point predictions of PM2.5 concentrations for the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air) using irregular monitoring data derived from the AQS regulatory monitoring network and supplemental short-time scale monitoring campaigns conducted to better predict intra-urban variation in air quality. We demonstrate the interpretation and accuracy of this methodology in modeling data from 2000 through 2006 in six U.S. metropolitan areas and establish a basis for likelihood-based estimation. (C) 2011 Elsevier Ltd. All rights reserved.
  •  
17.
  • Sheesley, Rebecca J., et al. (författare)
  • Source characterization of organic aerosols using Monte Carlo source apportionment of PAHs at two South Asian receptor sites
  • 2011
  • Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 45:23, s. 3874-3881
  • Tidskriftsartikel (refereegranskat)abstract
    • The quantification of source contributions is of key importance for proposing environmental mitigation strategies for particulate organic matter. Organic molecular tracer analysis of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes was conducted on a set of winter samples from two regional receptor sites in South Asia: the Island of Hanimaadhoo (the Republic of Maldives) and a mountain top near Sinhagad (W. India). Monte Carlo source apportionment (MCSA) techniques were applied to the observed PAH ratios using profiles of a representative range of regional combustion sources from the literature to estimate the relative source contributions from petroleum combustion, coal combustion and biomass burning. One advantage of this methodology is the combined use of the mean and standard deviation of the diagnostic ratios to calculate probability distribution functions for the fractional contributions from petroleum, coal and biomass combustion. The results of this strategy indicate a higher input from coal combustion at the Hanimaadhoo site (32-43 +/- 21%) than the Sinhagad site (24-25 +/- 18%). The estimated biomass contribution for Sinhagad (53 +/- 22%) parallels previous radiocarbon-based source apportionment of elemental carbon at this location (54 +/- 3%). In Hanimaadhoo, the MCSA results indicate 34 +/- 20% biomass burning contribution compared to 41 +/- 5% by radiocarbon apportionment of EC. While the MCSA based on PAH ratio diagnostic distributions are less precise than the radiocarbon-based apportionment, it provides additional information of the relative contribution of two subgroups, coal and petroleum combustion, within the overall contribution from fossil fuel combustion.
  •  
18.
  • Vogt, Matthias, et al. (författare)
  • Traffic Aerosol emission velocity derived from direct flux measurements over urban Stockholm, Sweden
  • 2011
  • Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 45:32, s. 5725-5731
  • Tidskriftsartikel (refereegranskat)abstract
    • Size-resolved aerosol vertical number fluxes were measured using the eddy covariance method, 105 meters above the ground over the city of Stockholm, Sweden, between 1st April 2008 and 15th April 2009. The size range of the measurements cover particles from 0.25 to 2.5 μm diameter (Dp). Emission velocities (ve) were calculated for the same size range and were found to be well correlated with friction velocity (u*) and CO2 fluxes (FCO2). These variables were used to parameterize the emission velocity aswhere ve and u* are given in [m s−1], Dp in [μm], and FCO2 in [mmol m−2s−1]. The parameterization reproduces the average diurnal cycle from the observations well for particles sizes up to 0.6 μm Dp. For larger particles the parameterization tends to over predict the emission velocity. These larger particles are not believed to be produced by combustion and therefore not well represented by FCO2, which represents the traffic source through its fossil fuel consumption and the related CO2 emissions.
  •  
19.
  •  
20.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 11-20 av 20
Typ av publikation
tidskriftsartikel (20)
Typ av innehåll
refereegranskat (17)
övrigt vetenskapligt/konstnärligt (3)
Författare/redaktör
Bellander, T (3)
Johansson, Christer (2)
Gustafsson, Örjan (2)
Andersson, August (2)
Lindström, Johan (2)
Sheesley, Rebecca J. (2)
visa fler...
Cyrys, J (1)
Pekkanen, J (1)
Calvo, E. (1)
Schneider, J. (1)
Gehrig, R. (1)
Perrino, C. (1)
Putaud, J. P. (1)
Simpson, David, 1961 (1)
Spindler, G. (1)
Danielsson, H. (1)
King, M. D. (1)
Peichl, Matthias (1)
Kiss, G (1)
Fischer, Andreas (1)
Braun, S. (1)
Linderholm, Hans W., ... (1)
Schwarz, J. (1)
Birmili, W. (1)
Wiedensohler, A. (1)
Struthers, Hamish (1)
Hansson, Hans-Christ ... (1)
Rodriguez, S. (1)
Smolik, J. (1)
Jeppsson, Knut-Håkan (1)
Pagels, Joakim (1)
Pleijel, Håkan (1)
Nilsson, S. (1)
Hansson, Per-Anders (1)
Vogt, Matthias (1)
Ahlm, Lars (1)
Pleijel, Håkan, 1958 (1)
Sandberg, Mats, 1945 ... (1)
Wichmann, J. (1)
Strandberg, Bo, 1960 (1)
Bauer, H (1)
Querol, X. (1)
Alastuey, A. (1)
Krusa, Martin (1)
Klingberg, Jenny, 19 ... (1)
Lindgren, Magnus (1)
Rosell, Lars (1)
Bäfver, Linda (1)
Larsson, Gunnar (1)
Langer, Sarka, 1960 (1)
visa färre...
Lärosäte
Stockholms universitet (4)
Lunds universitet (4)
Göteborgs universitet (3)
Karolinska Institutet (3)
Sveriges Lantbruksuniversitet (3)
Uppsala universitet (2)
visa fler...
Chalmers tekniska högskola (2)
Kungliga Tekniska Högskolan (1)
Högskolan i Gävle (1)
RISE (1)
visa färre...
Språk
Engelska (20)
Forskningsämne (UKÄ/SCB)
Naturvetenskap (11)
Lantbruksvetenskap (3)
Teknik (1)
Medicin och hälsovetenskap (1)
Samhällsvetenskap (1)

År

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy